1. Field of the Invention
The present invention relates to an apparatus and method for detecting defects in an image displayed on a display device such as a liquid crystal panel. In particular, the present invention relates to an image defect detection apparatus and an image defect detection method which involves acquiring an image displayed on a display device through imaging techniques, etc., to detect defects in the display device based on the acquired image. The present invention also relates to a storage medium in which a procedure of such an image defect detection is stored.
2. Description of the Related Art
Display screens, e.g., in the form of display panels, are required to provide uniform image quality across the entire screen. In any process for producing display panels, efforts are made to locate defects in display screens by visually inspecting actual images which are displayed on the display screens.
There are various kinds of defects that could occur on display screens, e.g., point defects (i.e., defects occurring in minute regions), stain defects and puddle defects (both of which may occur in sizable areas), and linear defects (which may occur in linear strips). Such a variety of defects are usually detected through visual inspection by a human inspector. However, even if the same inspector checks two display screens which actually provide the same level of image quality, the inspection results may vary depending on the proficiency or the physical condition of the inspector. Thus, inconsistent judgements may result, i.e., products that are considered as satisfactory on one day might be considered as defective on another day. Hence, it is difficult to provide consistent inspection results with a constant accuracy.
Therefore, impartial machine inspection systems are preferred over human visual inspection. However, since there are various types of defects, complete inspection requires a number of check items to be covered.
Japanese Laid-Open Patent Publication No. 9-9303 discloses a structure for inspecting the quality of images presented on a display panel by acquiring an image presented on the display panel and subjecting the image data to various processes corresponding to a number of check items.
However, since the structure disclosed in Japanese Laid-Open Patent Publication No. 9-9303 examines image data on a pixel-by-pixel basis, it only allows for the detection of minute point defects (i.e., defects contained in each pixel) where such point defects produce substantially lower outputs than do their surrounding pixels.
However, a point defect (i.e., a defect contained in a single pixel) often occurs with some degradation due to A/D conversion to which image data is subjected by an A/D converter, a decrease in the voltage level on various wiring, etc., and therefore may also be accompanied by a slight decrease in the outputs of the surrounding (i.e., upper, lower, right, and left) pixels. Therefore, any method that is based on the examination of the image data from only one pixel will have difficulties in locating such point defects.
As for puddle defects and the like, it is often the case that there is only a small decrease in the output from each pixel within the puddle defect area or like defect areas, so that the image data hardly shows any change with respect to each pixel. Therefore, even if such image data are compared against the image data presented by relatively distant pixels, it may still not suffice to accurately detect the puddle defects or the like.
There is also a problem in that, in color displays, a defect may occur as a result of one, or two or more, of the RGB components becoming abnormal, in which case it is difficult or even impossible to know which color component is actually malfunctioning.
Therefore, there is a need for a fast image defect detection apparatus which is capable of comparing a number of pixels at a time and which can realize detection abilities at the level of the human visual inspection.
The aforementioned problems may also arise in situations where there is a need to examine, through imaging of a given surface, whether or not a coating layer on the surface has been uniformly applied.
According to the present invention, there is provided an image defect detection apparatus including: an image acquisition section for acquiring an image as image data; a check section for checking for the presence or absence of a defect in the image, the defect being of one of a plurality of different types; wherein the check section includes: a matrix setting subsection for setting, within the acquired image, an inspection reference region and an inspection region in accordance with each type of defect; a comparison value extraction subsection for extracting a comparison value based on image data in the inspection reference region and image data in the inspection region as set by the matrix setting subsection; and a comparison subsection for determining the presence or absence of the defect based on a comparison between the comparison value extracted by the comparison value extraction subsection and a predetermined threshold value.
In one embodiment of the invention, the image data acquired by the image acquisition section is image analog data, and the image defect detection apparatus further includes an A/D converter for converting the image analog data into image digital data.
In another embodiment of the invention, the image defect detection apparatus further includes a color separation section for separating the image data into respective color components of a color system.
In still another embodiment of the invention, the image data is image digital data.
In still another embodiment of the invention, the image data is image analog data.
In still another embodiment of the invention, the color separation section performs a check with respect to each separated color component concurrently.
In still another embodiment of the invention, the predetermined threshold value is adjusted according to the respective color components of the color system.
In still another embodiment of the invention, the matrix setting subsection sets a location and a size for each of the inspection reference region and the inspection region, and a distance therebetween.
In still another embodiment of the invention, the matrix setting subsection sets the locations of the inspection reference region and the inspection region so as to adjoin each other in a case where the defect being checked for is a point defect, a stain defect, or a linear defect.
In still another embodiment of the invention, the matrix setting subsection sets the inspection reference region and the inspection region so as to be at a distance from each other in a case where the defect being checked for is a puddle defect, the distance constituting at least one pixel.
In still another embodiment of the invention, the matrix setting subsection sets the size of the inspection reference region and the inspection region at a first value in a case where the defect being checked for is a stain defect, a puddle defect, or a linear defect, and at a second value in a case where the defect being checked for is a point defect, the first value being greater than the second value.
In still another embodiment of the invention, wherein the inspection reference region and the inspection region are each defined as a block consisting of M pixels along a horizontal direction and N pixels along a vertical direction, and wherein M and N are natural numbers such that the relationship M=N=1 does not hold.
In still another embodiment of the invention, the image data acquired by the image acquisition section is image analog data, and the image defect detection apparatus further includes an A/D converter for converting the image analog data into image digital data, and at least one of M and N is set to a value in accordance with output characteristics of the A/D converter.
In still another embodiment of the invention, M=N in a case where the defect being checked for is a point defect.
In still another embodiment of the invention, M less than N in a case where the defect being checked for is a linear defect extending along a vertical direction.
In still another embodiment of the invention, M greater than N in a case where the defect being checked for is a linear defect extending along a horizontal direction.
In still another embodiment of the invention, a comparison position is shifted pixel by pixel within the inspection reference region and the inspection region, the comparison position being sequentially checked for the presence or absence of a defect in the image acquired by the image acquisition section.
Alternatively, according to the present invention, there is provided an image defect detection apparatus including: an image acquisition section for acquiring an image as image data; a plurality of check sections each for checking for the presence or absence of a defect in the image in parallel, the defects being of different types; wherein each check section includes: a matrix setting subsection for setting, within the acquired image, an inspection reference region and an inspection region in accordance with each type of defect; a comparison value extraction subsection for extracting a comparison value based on image data in the inspection reference region and image data in the inspection region as set by the matrix setting subsection; and a comparison subsection for determining the presence or absence of the defect based on a comparison between the comparison value extracted by the comparison value extraction subsection and a predetermined threshold value.
In one embodiment of the invention, the image data acquired by the image acquisition section is image analog data, and the image defect detection apparatus further includes an A/D converter for converting the image analog data into image digital data.
In another embodiment of the invention, the image defect detection apparatus further includes a color separation section for separating the image data into respective color components of a color system.
In still another embodiment of the invention, the image data is image digital data.
In still another embodiment of the invention, the image data is image analog data.
In still another embodiment of the invention, the color separation section performs a check with respect to each separated color component concurrently.
In still another embodiment of the invention, the predetermined threshold value is adjusted according to the respective color components of the color system.
In still another embodiment of the invention, each check section includes at least one processor for performing the checking.
In still another embodiment of the invention, one or more of the plurality of check sections is dedicated to checking for the presence or absence of a stain defect, a puddle defect, or a linear defect, and the one or more check sections each includes at least two processors for performing the checking.
In still another embodiment of the invention, the matrix setting subsection sets a location and a size for each of the inspection reference region and the inspection region, and a distance therebetween.
In still another embodiment of the invention, the matrix setting subsection sets the locations of the inspection reference region and the inspection region so as to adjoin each other in a case where the defect being checked for is a point defect, a stain defect, or a linear defect.
In still another embodiment of the invention, the matrix setting subsection sets the inspection reference region and the inspection region so as to be at a distance from each other in a case where the defect being checked for is a puddle defect, the distance constituting at least one pixel.
In still another embodiment of the invention, the matrix setting subsection sets the size of the inspection reference region and the inspection region at a first value in a case where the defect being checked for is a stain defect, a puddle defect, or a linear defect, and at a second value in a case where the defect being checked for is a point defect, the first value being greater than the second value.
In still another embodiment of the invention, the inspection reference region and the inspection region are each defined as a block consisting of M pixels along a horizontal direction and N pixels along a vertical direction, and wherein M and N are natural numbers such that the relationship M=N=1 does not hold.
In still another embodiment of the invention, the image data acquired by the image acquisition section is image analog data, and the image defect detection apparatus further includes an A/D converter for converting the image analog data into image digital data, and at least one of M and N is set to a value in accordance with output characteristics of the A/D converter.
In still another embodiment of the invention, M=N in a case where the defect being checked for is a point defect.
In still another embodiment of the invention, M less than N in a case where the defect being checked for is a linear defect extending along a vertical direction.
In still another embodiment of the invention, M greater than N in a case where the defect being checked for is a linear defect extending along a horizontal direction.
In still another embodiment of the invention, a comparison position is shifted pixel by pixel within the inspection reference region and the inspection region, the comparison position being sequentially checked for the presence or absence of a defect in the image acquired by the image acquisition section.
In another aspect of the present invention, there is provided an image defect detection method including: an image acquisition step of acquiring an image as image data; a checking step of checking for the presence or absence of a defect in the image, the defect being of one of a plurality of different types; wherein the checking step includes: a matrix setting substep of setting, within the acquired image, an inspection reference region and an inspection region in accordance with each type of defect; a comparison value extraction substep of extracting a comparison value based on image data in the inspection reference region and image data in the inspection region as set by the matrix setting substep; and a comparison substep of determining the presence or absence of the defect based on a comparison between the comparison value extracted by the comparison value extraction substep and a predetermined threshold value.
In still another embodiment of the invention, the image data acquired by the image acquisition step is image analog data, and the image defect detection method further includes an A/D conversion step for converting the image analog data into image digital data.
In still another embodiment of the invention, the image defect detection method further includes a color separation step of separating the image data into respective color components of a color system.
In still another embodiment of the invention, the image data is image digital data.
In still another embodiment of the invention, the image data is image analog data.
In still another embodiment of the invention, the color separation step performs a check with respect to each separated color component concurrently.
In still another embodiment of the invention, the predetermined threshold value is adjusted according to the respective color components of the color system.
In still another embodiment of the invention, the matrix setting substep sets a location and a size for each of the inspection reference region and the inspection region, and a distance therebetween.
In still another embodiment of the invention, a comparison position is shifted pixel by pixel within the inspection reference region and the inspection region, the comparison position being sequentially checked for the presence or absence of a defect in the image acquired by the image acquisition step.
Alternatively, according to the present invention, there is provided an image defect detection method including: an image acquisition step of acquiring an image as image data; a plurality of checking steps of checking for the presence or absence of a defect in the image in parallel, the defects being of different types; wherein each checking step includes: a matrix setting substep of setting, within the acquired image, an inspection reference region and an inspection region in accordance with each type of defect; a comparison value extraction substep of extracting a comparison value based on image data in the inspection reference region and image data in the inspection region as set by the matrix setting substep; and a comparison substep of determining the presence or absence of the defect based on a comparison between the comparison value extracted by the comparison value extraction substep and a predetermined threshold value.
In one embodiment of the invention, the image data: acquired by the image acquisition step is image analog data, and the image defect detection method further includes an A/D conversion step for converting the image analog data into image digital data.
In another embodiment of the invention, the method further includes a color separation step of separating the image data into respective color components of a color system.
In still another embodiment of the invention, the image data is image digital data.
In still another embodiment of the invention, the image data is image analog data.
In still another embodiment of the invention, the color separation step performs a check with respect to each separated color component concurrently.
In still another embodiment of the invention, the predetermined threshold value is adjusted according to the respective color components of the color system.
In still another embodiment of the invention, one or more of the plurality of checking steps is dedicated to checking for the presence or absence of a stain defect, a puddle defect, or a linear defect, and the one or more checking steps each includes at least two discrete substeps.
In still another embodiment of the invention, the matrix setting substep sets a location and a size for each of the inspection reference region and the inspection region, and a distance therebetween.
In still another embodiment of the invention, a comparison position is shifted pixel by pixel within the inspection reference region and the inspection region, the comparison position being sequentially checked for the presence or absence of a defect in the image acquired by the image acquisition step.
In yet another aspect of the present invention, there is provided a storage medium in which a procedure of an image defect detection method is stored, the image defect detection method including: an image acquisition step of acquiring an image as image data; a checking step of checking for the presence or absence of a defect in the image, the defect being of one of a plurality of different types; wherein the checking step includes: a matrix setting substep of setting, within the acquired image, an inspection reference region and an inspection region in accordance with each type of defect; a comparison value extraction substep of extracting a comparison value based on image data in the inspection reference region and image data in the inspection region as set by the matrix setting substep; and a comparison substep of determining the presence or absence of the defect based on a comparison between the comparison value extracted by the comparison value extraction substep and a predetermined threshold value.
Alternatively, according to the present invention, there is provided a storage medium in which a procedure of an image defect detection method is stored, the image defect detection method including: an image acquisition step of acquiring an image as image data; a plurality of checking steps of checking for the presence or absence of a defect in the image in parallel, the defects being of different types; wherein each checking step includes: a matrix setting substep of setting, within the acquired image, an inspection reference region and an inspection region in accordance with each type of defect; a comparison value extraction substep of extracting a comparison value based on image data in the inspection reference region and image data in the inspection region as set by the matrix setting substep; and a comparison substep of determining the presence or absence of the defect based on a comparison between the comparison value extracted by the comparison value extraction substep and a predetermined threshold value.
Thus, according to the present invention, it is possible to provide detection abilities which cover various check items, e.g., point defects, stain defects, puddle defects, and linear defects, that are accomplished conventionally by human inspectors. It is also possible to break down an acquired image into color components (e.g., RGB) to detect which specific color component has become abnormal. It is also possible to provide an evaluation for each entire display screen based on the size and/or shape of the inspection region versus an inspection reference region, according to the needs of the various defect checks. It is also possible to perform a quick inspection process that covers a number of check items for each color component simultaneously. Thus, it is possible to provide fast and accurate defect detection without imposing any requirements on the proficiency or physical condition of a human inspector, thereby contributing to improvement in production yield and product quality of display apparatuses.
Thus, the invention described herein makes possible the advantages of (1) providing a fast and accurate method and apparatus for image defect detection which is capable of detecting various defects without imposing any requirements on the proficiency or physical condition of a human inspector: and (2) providing a storage medium in which a procedure of such an image defect detection is stored.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.